Terms Starting with Letter: V vascular endothelial growth factor (VEGF) VEGF is a protein that binds to epithelial cell receptors promoting their growth, stimulating angiogenesis, and increasing permeability of the endothelium. vector An agent (e.g., liposome or virus) or plasmid that can be used to deliver a gene to an organism. virus Any of various submicroscopic pathogens that are without metabolism and are capable of growth and multiplication only in living cells.